Vibrating screen



June 26, 1923. 1,459,839

B. A. MITCHELL A VIBRATING SCREEN Original Filed 001:. 16. 1918 4Sheets-Shet l June 26, 1923. I 1,459,839

B. A.- MITCHELL VIBRATING SCREEN Original Filed Oct. 16. 1918 4Sheets-Sheet 2 H] WP. l l H 1 I or 2/ 2Q 2 [a ll fi amzjfliz g a I ATTORNEYJ yum 26,1923. Mw'w y B A. NHTCHELL VIBRATING SCREEN ori inalFiled Oct. 16. 1918 4 eets-Sheet 5 June 26, 1923;

B. A. MITCHELL VIBRATING SCREEN Original F iled Oct. '16. 1918 4Sheets-Sheet 4.

Patented June 26, 1223.

NETF.

FFEQE.

BENJAMIN A. MITCHELL, ST. GEORGE, NEW YORK, ASSIGNOB 0F TWO-THIRDS T0MINNIE L. MITGEELL, 0F MAGNA, UTAH.

VIBRATING SCREEN.

Application filed October 16, 1918, Serial 310.25%,466. Renewed May 1'7,1923.

To all whom, it may concern.

Be it known that I, BENJAMIN A. Mrrorn ELL, a citizen of the UnitedStates, residing at St. George, Staten Island, in the county of Richmondand State of New York, have invented certain new and useful Improvementsin Vibrating Screens, of whic the following is a specification.

This invention relates to vibrating screens and more particularly toscreens actuated -for sifting ore, sand, gravel and the like.

This invention has for its general object an improved construction andarrangement of parts which is durable, eflicient, and readilymanufactured.

A more specific object of. this invention is to provide improvedapparatus of this character for carrying out screening processes withoutclogging.

Another object is to provide an arrange ment in which the screen for thematerial to be screened is actuated by a vibrator utilizing theprinciple of rotating moments.

Another object is to provide improved means for applying to screensunder tension, a harmonic motion of constantly changing direction.

Another object is to provide means for setting up vibrations of uniformamplitude throughout the width of screens.

Another object is to provide means for imparting vibrations in differentphases to different partsof a screen,

Still another object's to provide improved means for connectingvibrators in operl'ative relation with the screen to be actuate Otherobjects and advantages will in part be specifically pointed outhereinafter and.

in part obviousfrom the arrangements and constructions here set forth.

The invention'accordingly consists in the features of construction,combinations of elements and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scopeoftheir ap-- plication will appear in the appended claims.

For a more complete understanding of the nature and advantages of thisinvention reference should be had to the following detailed description,which describes the best illustrative embodiments of this invention atpresent known to me, taken in connection with the accompanying drawingin which:

Fig. 1 shows a front elevation of screening apparatus embodying theimprovements of my invention;

Fig. 2 shows a vertical sectional view taken on the line 2-2 of Fig. 1,looking in the direction of the arrows;

Fig. 3 shows an enlarged view of the vibrator and the means forconnecting the same to the screen, part of the vibrator being shown inlongitudinal section:

Fig. 4: shows anenlarged end view of the vibrator, illustrating themeans for transmitting vibrations from the vibrator to the screen;

Fig. 5 shows an enlar,ed sectional view of the means for holding t eopposite edges of the screen; I

Fig. 6 shows an enlarged central vertical sectional view through thevibrator taken on the line'66 of Fig. 3;

Fig. 7 shows a vertical sectional view similar to Fig. 2, illustrating amodified arrangement of the apparatus;

Fig. 8 shows a' vertical sectional view tlllfllgh thevibrator-illustrated in Fig. 7, an I Fig. 9 shows a longitudinal view ofthe vibrator illustrated in Fig. 7.

Referring now ,to the drawing, and to Figs. 1 and 2 in particular, 20denotes ahopper or other device supported in operative relation with avscreen 40 which is adapted to feed the material to be screened throughan outlet23 controlled by a gate .24:

onto the upper part of the screening sur' face. The supporting structurefor the hopper as shown comprlses aframe composed of members 21 and 22,which in addition supports the screen-frame 30- holding the screen 40the vibratin means or vibrator 46 for the screen 40a so being supportedat tit) one side of the plane of the screen by this structure. Thepressure vof the material within the hopper tends normally to open thegate 24, and the degree of opening of the gate is controlled by abolt-26 whichpasses through oneof the bars 25, and is enga ed atitsouter end by a winged-nut 27. he

loose material falling through the outlet.

opening 23 passes onto the screen 40 which is, held his screen-frame 30the latter being hinged along its upper edge at the'points 31 on thesupporting frame of the apparatus. The screen-frame is shown asconstructed of angle bar members or other suitable parts, forming arectangular structure. The lower edges of the screen-frame 3Oareprovidedframe members 22. The bolts 35 may be caused to engage anydesired aperture34, so

that the lower edge ofthe screen-frame can be raised or lowered tochange the incline.-

tion of the screen, as desired. The material passing onto" the screen isscreened in the manner hereinafter described, so that the finely dividedmaterial passes downwardly into a chute or hopper 36, while the coarsematerial passing ofl the lower edge of the screen falls into anotherchute or hopper 37.

The screen 40 is mounted within the rectangular frame. 30, as shown inFig. 1, and the opposite ends of the screen cloth are secured to theframe by an adjustable device illustrated more particularly in Figs. 3and 5. The edge of the screen cloth is "wrapped around a circular rod 41located within a longitudinally slotted tube 42 with the over-. lappingparts of the screen extending outwardly through the slot, as illustratedin ig. 5, so that when the tubes 42*at opposite edges of the screen arepulled apart, the edges 42 of the slots press the screen against therods 41 and cause the same to be securely gripped. The tubes 42 areengaged by bolts 43 having arms 43 which extend partially aroundthe'tubes 42, as shown in- Fig. 3. These bolts pass through apertures inthe. walls of the screen frame 30 and are threadedly engaged by theadjusting members 44, so that the-screen can be stretched tightly withinthe frame and maintained continuously under relatively great tension,'substantially similar to a drum-head, through out the screeningoperation. As the screening process is carried on, it may be desirablefrom time to time to tighten the screen or to adjustthe tension thereofto secure the most desirable results with the particular material beingscreened, and it is found in,

practice that the desirable tension of the screen will de end also uponits weight and stifl'ness. Wit particularly heavy'and rigid screens, itis found that it is merely necessaryto support the screen firmly withinthe frame with suflicient rigidity to prevent any considerable downwardbending thereof and to maintain the same in a substantially rigidinflexible condition similar to the condition of a flexible screenstretched to a drum-head tightness. If desired, suitable guards 45 maybe mounted along the lateral edges of the screen to prevent the materialfrom passin over these edges.

he screen 40, as indicated, is stationarily supported so asto bevibrated independently of'the screen-frame 30; this being accomcentresand utilizes the principle of rotating I moments to produce relativelyminute vibratory movements of constrained amplitude having" a constantlychanging direction as set forth in my copending application Serial No.275,321. As illustrated the vibrator 46 comprises a central casing 47having bolted thereto the two end casings 48, each of which isreinforced by the longitudinally extending ribs 49. The central housinghas its base 47 mounted on a supporting beam 50 which is secured to themiddle part of the lower wallof the screen-frame 30 and extends inwardlytherefrom over the screen. A shaft 51 passes through the central housing,50' and has keyed thereon a pulley 52 which is adapted to be engaged bya belt 53 extending to a motor or other driving means. If desired, thehousing 47 may be made the casing of a motor and the armature of themotor mounted directly on the shaft, as hereinafter described. Thedetails of the construction here employed are more clearly illustratedin Figs. 3 and 6. So shown it comprises complementary portions securedtogether to form the housing 48, each portion of which is the same sothat one set only willtherefore be described. Mounted within eachhousing 48 is a bearing ring 54 having a hard metal collar 55 secured tothe outer side thereof and adapted to coact with balls '56, which run ina raceway formed by the annular collar 57 secured within the housing 48.Each end of the shaft 51 is reduced in diameter, and the reduced portionis keyed in a suitable recess formed in'an unbalanced rotary member 58having a lateral projection 59 on one side thereof. The lack of balanceof this rotary member is further increased by provlding an eccentricallylocated aperture 60 therethrough opposite the projection 59. Hard metalbearing collars 61 are secured to the ends of this unbalanced member,and these collars coact with balljections adapted tobear against therounded I surfaces of the hard metal caps 64, which are secured to theend walls 48 of the housing. The space within each end housing 48 isfilled with oil, or other lubricant, which is introduced throughaperturesclosed by the plugs 65. The rotation of the shaft 51at highspeed produces high frequency vibrations in the casing due to therotation of the unbalanced members 58.

The vibrations set up by the vibrator are imparted to the screen 40 bymeans of transmitting plates or membe s 6.8 whi h are carposite walls ofthe casing to be en illustratedlin the ried by the collars 69. The endsof the arts 48 of the vibratin casing are tapere as d awings, and theseportions. are adapted to be closely fitted by the correspondinglytapered walls of the rings 69. Apertures are provided through the op.-ged by the transverse ke s 70 by which t e rings 69 are securely c ampedin position. The rings 69 are rigidly secured to the transmittingmembers 68 by means of rivets or the like 71, and these transmittingmembers are in the form of relatigely long plates as illustrated inFigs. 1, 2;? and 4, extending substantially across the screen in adirection transverse to the axis of rotation of the unbalanced rotarymembers. The lower edges of the transmitting members compriselongitudinally extending blocks or strips 72 of wood, or otherequivalent material,-which strips bear directly upon the upper surfaceof the screen, as illustrated more particularly in Fig. 3, but whichstrips are not secured to the screen. The parts are so proportioned thatthe strips 72 bear rigidly against the screen surface, however, when thelatter is in a rigid or substantially inflexible condition, as when aflexible screen is stretched to a substantially drum-head tightness, sothat the vibrations set u the casing of the vibrator are impartedirectly to the screen. The screen thus vibrates a high frequencyindependently of the frame in which it is mounted, and produces athorough screening of the material which passes downwardly thereover.

Instead of employing the arrangement illustrated in Figs. 1 to 6,inclusive, it may be desirable in some instances to use the arrangementof apparatus illustrated in Figs. 7 to 9, inclusive, wherein thevibrator and its directly connected parts are mounted beneath thesurface of the screen, thus leaving the space above the screen entirelyfree'and unobstructed. In this modification, a supporting frame,comprising the vertically extending members 7 5 and the horizontalmembers 76, carries a hopper 7 8 from which the material is fed by agate 79 onto an inclined screen 80 mounted in the screen frame 81, whichis hinged at the points 82'and supported at its lower end by means ofadjustvibrator 85 has a central housing 86 which forms a casing of anelectric motor, and the base 86 of this motor 'is' secured to asupporting beam 87 which i seemed to th lower part of the'screen frameand'extends upclamping rings 90 mounted on the erfids thereof aretransmitted to clamping members 91 which extend upwardly and bearagainst the underside of the screen b means of the intermediate strips92 of woo or the like. This arrangement of the apparatus is similar tothat previously described, in that thecentral housing is mounted on apart which is rigid with the screen frame, while the projectingandvibrating ends of the easing are operatively connected directly to thescreen. The central housing in the last described embodiment isentirelyv closed, however, to prevent the access of dust to the interiorof the vibrator, and this construction has the advantage that the screenbears downwardly upon the transmitting members, so that the weight ofthe material on the screen tends to increase the contact between thescreen and the transmitting mem-- bers, whereas, in the first form ofthe invention described, the weight of the material tends to separatethe transmitting members from the screen. The-second invention has thefurther feature that it leaves the upper surfaceof thescreen entirelyunobstructed. If desired, the vibrator of the second form ,of theinvention may be further enclosed by a supplementary sheet metal housing'93.

With each form of the invent on it is found that improved results areobtained in the screening of crushed ore and other ma-v terials, due tothe novel combination of the vibrating means and the screen. Due to theaction of the rotary vibrator, which is in direct connection with thescreening medium, each and every particle of the screen vibrates in an.extremely small circle, so that a vibration is set up in the screenwhich is in some respects the combination of a vibration transversely ofthe screen and a vibration in the plane of the screen. This I serves tosift the materials over the screen surface as they pass downwardlythereover by gravity, and to effect a more perfect screening action thanis possible with any form of screening device heretofore known. By theuse of my improved vibrator it is possible to produce two series ofvibrations in the screen through the two transmitting plates which areconnected, to opposite ends of the vibrator casing. The unbalancedrotary members in opposite ends of the vibrator casing are pre erablymounted 180 apart on the shaft, so that the vibrations p duced therebyare rm wherebytheactionxsg v: 1mproved. The and secon vibrations produ yin the screen by the operation ofthe rotary vibrator aresu rim upon eachother, so that m a rotation at the rate of 3600 revolutions minute it isbelieved to be easily possible to.

obtain in the screen vibrations of-about 18,- 000 or 20,090 per minute.This hi frequency of the vibrations produced directly in the screenmakes, it im terials to become clo v r m the meshes of the screen, andthus t e invention overcomes the difliculty which has been present inall prior screen devices of which ap licant is aware. Even when the wdeore, or other material, iswet, it is found that the high frequencyvibrations in the screen prevent the material from adhering to themeshes of the screen and, at the same time,

the materials fed to the screen pass therethrough at a more 'rapid ratethan is powble with the ordinary scree" devices. The unbalanced rotarvibrator as the advantage that it pro uces a high frequency vibrationwithout embody' cumbersome or complicated apparatus, an the frequency ofvibrations may be readil fiivaried by v the speed of rotation. frequency0 the vibrations in the screen may also be regulated by adjusting thetension of the screen, and although the desirable degree of tightness ofthe screen may vary under different circumstances, it ispreferred tostretch it to an extremely tight condition, approximating the tightnessof a drum-head. In order to secure the best results with'any given feedZ of material, it is desirable to ad ust the tension of the screenaccording to the rate of rotation of the vibrator and to the rate offeed of the material. With extremely heavy screens rigidly mounted inthe frame, the vibrations produced are similar to those obtained with alighter screen stretched to and maintained under extremely hi h'tension.

Although I have shown and escribed certain embodiments of the inventionfor purposes of illustration, .itwill be understood that it may beconstructed in various different forms without departing from the scopeof the a pended claims.

What I claim is:

L In apparatus of the class described, an inclined screen supported insubstantially fixed position, and means for producing in said screen aplurality of simultaneously acting series of minute circular vibrationsin planes perpendicular to the plane of the screen.

' 2. In apparatusof the class described, an inclined screen, and meansfor producing a plurality of series of minute circular vibra. tionsdirectly in said screen in planes perpendicular' to the plane of thescreen, said bio for mainclined screen, a vibrator casing, means 'forproducing minute circular vibrations in said casing, and means fortransmitting a plurality of simultaneously aotiigrzeries of saidvibrations to said screen ughout the width of the screen.

4. In apparatus of the class described, a screen, means for hol .saidscreen in a diff rigid condition, a vibrator casing located outwardlyfrom the plane of said screen, means for producing minute circularvibrations in said casing, and arigid transmitt' plate carried b saidvibrator and contacting edgewise wit said screen.

5. In apparatus of the class described, a screen, means for hol saidscreen ina stifi rigid condition, a vibraton casing located outwardlyfrom the plane of said screen, means for reducing minute circularvibrations in casing, and a pair of transmitting plates connected to theends of said casing and bearingi edgewise on said screen throughout itsW1 th.

6. In apparatus of the class described, a screen, means for hol said"screen and maintaining the same un er a tight drumhead tension, andmeans for producing a plurality of series of continuous vibrations ofuniform amplitude across said screen in means for producing tension insaid screen,

and means for producing aseries of continuous circular vibrations insaid screen in a plane perpendicular tothe plane of the screenindependently of said frame.

8. In apparatus of the class described, a frame, a screen mounted insaid frame, a supporting member .pro'ecting from said e substantiallypara e] to said screen, and a rotating vibrator movably carried'by saidsupportin member arranged and connected to the intermediate portion ofsaid screen for transmitting thereto harmonic motions executed in a"plane transverse to the plane of said screen.

9. In apparatus of the class described, a screen stationarily supportedin screening position, a vibrator having a pair of rotatmg eccentricmass centres disposed in different bases, a support for said vibratordisposed between sa1d centres, and means on said vibrator for-impartingvibrations to said screen.

10. In apparatus of the class described, a

screen stationarily supported in. screening position, a vibratoractuated internally by a rotating moment for producing relatlvely minutevibrations executing a sad orbit a sup ort for said vibrator atone sideof the p ane of the screen, and means for n11- parting said vibrationsto a plurality of portions of said screen.

said screen, and means for producing and maintaining tension in saidscreen.

13. In apparatus of the class described, a. frame a screen mounted insaid frame m a substantially rigid inflexible condition, a

rotary vibrator carried by said frame between the edges of said screenand having a double oscillatory motion with respectwto its support, andrigid means connecting the end portions of said vibrator with saldscreening medium. 0

14. In apparatus of the class described, a screen, a supporting memberat one slde of the plane of said screen, a rotating vibrator having adouble vibratory movement about its centrally fixed support on saldsupporting member, a rigid plate connected to sald vibrator and havingone edge bearing against said screen, and means'for operating saidvibrator.

15. In apparatus of the class described, a screen frame, a screendetachably mounted on said frame, a rotating vibrator having a doubleoscillation about its central support mounted opposite the. middle partof said screen, and transmitting means detachably mounted on saidvibrator and bearing against said screen and transmitting to said screencircular vibrations in a plane perpendicular to said screen.

16. In apparatus of the class described,

an inclined screen, means for feeding loose materials to the upperpartof said screen,

means for producing tension in said screen, a rotating'vibrator mountedindependently of said screen, and means for transmitting two series ofuniform, circular vibrations forming a continuous operative connectionbetween said vibrator and said screen and per .endicular to said screen.

1 In apparatus of the class described, a screen, a vibrator cas' mountedopposite said screen, said casing avi two tubular parts, a ring securedon each c said tubular arts, and plates carried by said aringlon saidscreen perpendicular y.

18 apparatus of the class described, a

and,

screen, a rotating vibrator having a double oscillating motion about itscentral support" mounted opposite the central part of said screen,plates attached to the ends of said vibrator and' bearing on saidscreen. per- .pendicularly, and means for operating said vibrator.

19. In apparatus of the class described, a screen stationarily supportedin screening position, a vibrator having a pivoted cen tral portion andend portions adapted to. execute vibrationsof constrained amplitude andconstantly changing directions phases displaced by 180 degrees, rigidmeans on said end portions for transmitting said vibrations to saidscreen, and means for iiitroducing material to be upper surface.

20.v In apparatus of the-class described,

a screen, a rotary vibrator comprising an.

electric motor having unbalanced rotary members on each end of its shaftone hundred and eighty degrees apart, and rigid members transmitting thecharacteristic vibrations of said vibrator to said screen in a planeperpendicular to the plane of said screen.

screened upon its so i 21. In an apparatus of the class described,

a screen, means for stationarily supporting said screen in an inclinedposition, means for producing minute circular vibrations in the body ofsaid screen, and means for. passin loose materials to the upper part ofsaid screen.

22. In an apparatus of the class described,

directly in said screen and in a plane perpendicular to the plane ofsaid screen.

23. In apparatus of the class described, a screen, means for maintainingsaid screen in I a stiif rigid condition, means for supporting saidscreen in an inclined position, means for introducing loose materialsonto the upper part of said screen, and means located opposite the planeof said screen and having a connection therewith for producing minutecircular vibrations of high frequericy directly in said screen andperpendicular to its plane of support.

24. The combination in a screening machine, of a rotary vibrator, meansfor supporting said vibrator at its center, transmitting platesconnected to the free end portions of saidvibrator and a screen clothextending over and vi rated by said transmitting plates.

25. combination in a. screening ms leaving the end portions thereof freeto vibrute, means for producing minute circular vibrations of frequenc;in the end portions of said casing, transmitting plates con nected tothe end portions of said casing, a screen cloth extending over saidtransmitting plates, and means for retaining said screen. cloth on saidplates and producing tension therein. J

In twtimony whereof, I have subscribed my name. 4 7' BENJAMIN A.MITCHELL.

